It is well known that the joining of textile materials is a frequent step in the textile industry. This applies particularly to continuous processing of textile webs, where textile webs must be joined to one another. In continuous or semi-continuous methods, the webs which have been processed are not completely pulled out of the machine but a new, fresh web is joined to the web end. In this manner, the processing machine is not run without any web therein which would create serious and very complicated problems including a standstill and a thorough cleaning of the machine and the tedious draw-in of the new web.
Throughout the present specification and claims, the expression "textile web" or "textile material" signifies any fibrous material which is linearly bidimensional, i.e. wherein the thickness of the material has a very small value compared with the breadth and, much more, with the length of the material. A typical range of the relative thickness: breadth (width): length is about 1:100-2500:1000-2,500,000. Such textile webs may be woven or non-woven fabrics, fleeces, knitted materials, and also monolayer or multilayer webs formed by parallel, sheet-like arrangements of yarns such as warp yarns.
The processing methods and apparatus for textile webs are well known to the man skilled in the art. Such kinds of processing methods are, e.g., the washing, gassing, dressing, bleaching, dyeing, printing, livening, finishing etc. Yarn sheets are generally sized and dyed.
Since it is known how to process sheets of parallel yarns in great working widths and since the uniform tension in all such individual yarns can be better maintained due to better yarn quality, the general trend is to use the yarns instead of the finished fabric for all processing operations as far as this is useful and reasonable in view of any further process steps. Thus, one would try to perform cleaning, bleaching, washing, shrinking, swelling, dyeing (especially vat dyeing), optical brightening, livening, softening, hydrophobing, flameproofing, shrinkproofing and, of course, sizing on said sheets of parallel yarns. Such methods are disclosed in Swiss patent No. 612,557 and French patent No. 1,201,724.
The hitherto known methods in this field suffer from serious difficulties. In fact, it is complicated and time-consuming to draw the yarns into the processing machine or into the set of machines arranged in series for the first time and when fresh yarns must be drawn in, to replace the feed. It must be taken into account that the number of parallel yarns in these machines is very high and amounts in most cases to from 7,000 to 10,000. The length to be drawn in can reach considerable values, of 350 meters or more.
This difficulty does not exist to the same extent in fabrics. In this case, the leading end of the new fabric is simply joined to the trailing end of the fabric under treatment by one or more transverse seams which can rapidly be made with a stand-by hand sewing machine.
Tests have shown that this solution cannot be used with textile materials which unravel in longitudinal direction (thus in the direction of drawing) like fleeces and, especially parallel yarns. Therefore, other possibilities for joining yarns in the lengthwise direction have been considered.
One possibility would be to knot each of the fresh yarns to be drawn into the machine to each one of the yarns already in the machine. But this kind of joint would be impossible to be made in practice, even if a knotting machine were available, in view of the time delay. Furthermore, it has been proposed to join both sets of yarns by a clamp bar applied transversally over both yarn sheets to be joined. This temporary joint has the drawback that its pulling speed through the machine would be insufficient. Besides, a clamp bar would be too bulky to be drawn through such machines.
The inventors had first considered to resolve the problem of forming a joint between such textile materials by introducing an intermediate joining element in the form of a fabric between the two yarn groups to be joined. This intermediate element would be affixed to the trailing and of the yarns under processing and would be drawn through the machine. Then, the leading ends of the fresh yarns would be fixed the trailing end of the intermediate fabric, and the fresh yarns could be introduced into the machine when said intermediate fabric is pulled out of the machine. However, there were no means or devices available to fix a sheet composed by thousands of parallel yarns in a satisfactory manner to a fabric having substantially the same width as said sheet.